The present invention generally relates to a method for reducing or eliminating an ammonia odor associated with hydrolysis of aluminum nitride powder upon exposure thereof to atmospheric moisture. The present invention more particularly relates to placing aluminum nitride powder in operative contact with certain organic compounds that react with or getter ammonia generated by said hydrolysis. The present invention also relates to the resultant operative combination or treated powder.
Aluminum nitride exhibits certain physical properties that make it particularly suitable for use in a variety of applications. Some applications, such as those in packaging components for electronic circuitry, require substantially full theoretical density and high thermal conductivity. High quality aluminum nitride powder, when densified by sintering, hot-pressing or other suitable means, generally satisfies these requirements.
Aluminum nitride powder readily reacts with water or hydrolyzes to liberate ammonia. Even moisture present in air is sufficient to initiate at least localized hydrolysis. Ammonia, even in very low concentrations, has a sharp, intensely irritating odor. In much larger concentrations, inhalation may be harmful or fatal.
Attempts to minimize ammonia production focus largely upon imparting moisture resistance or oxidation resistance to aluminum nitride powder surfaces. JP 63-225507, for example, forms a hydrophobic film on powder surfaces by using one or more different compounds selected from among fatty acids, fatty acid amides, and aliphatic primary or secondary amines. The compound(s) should contain at least 12 carbon atoms and be adsorbed to the surface of the JP 2-88412 adsorbs an aromatic carboxylic acid on the surface of aluminum nitride powder to increase its resistance to oxidation by moisture in the air during handling or storage operations. JP 64-61304 treats surfaces of direct nitrided aluminum nitride with a surfactant to improve oxidation resistance. The surfactants include aliphatic carboxylic acids such as stearic acid and oleic acid, aliphatic carboxylic acid salts or esters, higher alcohols, sulfonic acids and Lewis acids. JP 62-264077 treats aluminum nitride powder with 0.05 to 5.0 wt % of a compound represented by a formula CH2.dbd.CXY where X is an aryl group, a substituted aryl group, a benzyl group, a substituted benzyl group, a styryl group or a substituted styryl group, all substituents have 1 to 5 carbon atoms, Y is a hydrogen atom of X. Styrene and methyl styrene are particularly preferred compounds. JP 63-51607 adsorbs one or more different monohydric alcohols onto the surface of aluminum nitride powder. Monohydric alcohols have a carbon number of one to 18.
It would be desirable if there were a simple, yet effective means or method of neutralizing, gettering or otherwise reducing or eliminating ammonia generated by hydrolysis of aluminum nitride powder upon exposure to atmospheric moisture.